Hancock, Ghoulish Mayor is a rare Legendary Creature — Zombie Mutant Advisor card from Fallout (PIP), collector number 910. Current market price: — (foil $9.30), TCGplayer market prices via Scryfall.
Each other creature you control that's a Zombie or Mutant gets +X/+X, where X is the number of counters on Hancock. Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)